Wireless transmission system



Sept. 25, 1934. s s T v 1,974,545

WIRELESS TRANSMISSION SYSTEM Filed Dec. 4, 1931 "LL1 1 9 Y 20 SALVATORE 5ALTO- INVENTOR ATTORNEYS Patented Sept. 25 1934 WIRELESS TRANSMISSION SYSTEM Salvatore Salto, Milan, Italy :Application December '4, 1931, Serial No. 578,962

a In Italy December 5, 1930 8 Claims; (01; 250-11) This invention relates to a system for radiating energy by means of electromagnetic waves so as to concentrate a maximum of radiation in a given direction so that the receiving station-will 5 collect a maximum of energy, and particularly involves a system in which directional emission is obtained by producing a rotating electromagnetic wavedisturbance which is capable of being intercepted and detected by the mentioned receiving station.

The main object of my invention is to produce electromagnetic waves polarized in a circular manner, which waves are produced in a reliable manner absolutely regular in form.

Another object is to so propagate radiating energy in a given direction thatthe transmitted signals shall not be intercepted by receiving stations located in other directions than that of the transmitted wave. 1

A further object is to provide a system of directional wireless transmission adaptedfor emission of a modulated or unmodulated rotary electromagnetic field by using aerials or aerial components which are excited by a progressive wave flowing in a circuit coupled with said aerials or aerial components, 1

Other objects andthe various advantages inherent in the nature and embodiment of my invention will appear more fully in detail as the specification proceeds.

In the accompanying drawing forming part hereof,

Figure 1 is a diagram illustrating a basic principle of my invention.

Figure 2 illustrates an embodiment of my invention in one simple but practical form.

As already indicated the system constituting the present invention involves a special arrangement of antennae and their components.

The system advantageously comprises a plurality of aerials disposed radially of a common point and located substantially in a plane perpen- "di'cular 'toithe directionoof transmission andthe progressive wave may be applied by use of a coil preferably of ring formation disposed about such common point. The wave traverses'the coil in such fashion that a complete wave with its maxima and minima is included in the ,coil and such wave, in traversing the coil, sets up an electromagnetic field which turns about an imaginary axis perpendicular to the plane of the coil. Each aerial is coupled either inductively or capacitatively with the coil and'is consequently excited with a phase displacement corresponding to its point of coupling with the coil. Thus, if these couplings are distributed equally along the length of the coil, that isif the aerialsare equi-angularly spaced, therewill be set up in the aerials, a progressive excitation which willpass successively from 'a maximumto a minimum and these max ima and minima will bealways displaced 180 with respect to each other in diametrically opposite aerials which will thus have the same excitation butof opposite phase. At the same time, each aerial will pass successively through all its values gradually from a maximum to a minimum. The system provides an electromagnetic field polarized in circular sensercomparable to that of a ray of light, if one considers a single .one or" the innumerable vibrations of, which a ray of light is composed. The properties of these electromagnetic vibrations are such that they maintain their direction: of propagation, which in the present caseisperpendicularto theplane 'oftheaerials, and are able to serve-very well for connectingtransmitting and receiving stations either for radio-telegraphic or radio-telephonic signalling purposes or for transmitting electromagnetic energy through space.

Referring again to the drawing, it'has already been mentioned that Figure 1 illustrates the basic principle of the invention, wherein it may be seen that the transmission system primarily involves a series of simple aerials or aerial components such as '1, 2, 3, 4 which radiate in the form of a star froma central point which is grounded, and disposed vertically soasto face the receiving system.

While the latter is illustrated as a Hertz resonator 5, it might on'the other hand be a Marconi 96 aerial properly tuned to the length of the carrier wave ofthe transmission system or apparatus. The mentioned receiving system will oscillate if it is encountered by this radiation and will transmit potential variations to a detector device 6. If the carrier wave is modulated during transmission, it will be [possible to detect the modulation of .said .wave by means of an ordinary receiving system, whether it be a telephonic or telegraphic receiver, and to use the 100 received energy either as electrical energy or as mechanical energy after conversion by suitable means. The aerials l, 2, 3, 4 areof a length equal to one quarter of the wave and in practice are excited in such a mannerthat between any one of them and the next, there is a phase displacement. of a quarter the wave length, so that the anti-node of maximum positive potential at the end of the aerials obtains successively on,ifor instance, aerials, 1, 2,73, 4,.1, 2, 3,4, and

so on, whilst at the same time the anti-node of the maximum negative potential passes from aerials 3, 4, 1, 2, 3, 4, 1, 2 and so on. Such an arrangement will produce a rotary electromagnetic wave which will travel along an imaginary axis theoretically at right angles to the plane of the aerials. Deviation from said direction may be subsequently produced by the conductivity of the earth and by the magnetic field thereof, but if the effects of these are previously known, it is possible to direct the beam in the desired direction by making an appropriate correction. For the emission of the rotary electroe magnetic field, it would theoretically be sulficient to have three aerials suitably excited with a displacement of phase but in practice the number of aerials may be greater as indicated by Figure 1 and also by Figure 2 which shows diagrammatically a transmitter with eight aerials 8, 9, 10, 11, 12, 13, 14, 15 arranged in the formof a star in a vertical plane with angles of included between the aerials.

The aerials illustrated in Figure 2 may be excited by means of a coil 17 of ring formation which is suitably dimensioned to constitute the source of a complete progressive wave generated by an oscillator '7 and modulated by a microphone 16 in order to produce the mentioned progressive wave in accordance with the principles of the invention. For the purpose of insuring that the wave in the exciting circuit shall be progressive, characteristics of the coil should be such as to correspond with the following formula:

where R is the resistance of the circuit 17, 19, 18, 16, 7; L the self-induction of such circuit and C the capacity. (The parts 18, 19 are hereinafter referred to.) The propagation speed of the wave .along the coil can be deduced from Lechers expression, or from the general formula of the propagation theory, or by experiment.

The maxima and minima of the carrier wave travel through all of the turns of the annular coil and create a complete Wave travelling along the turns of the coil. The aerials coupled inductively or capacitatively to said coil receive impulses with phase displacements corresponding to the points of coupling thereto and as said points are uniformly distributed along the coil, the aerials are excited with equal phase displacements.

Of course care must be taken that the constants of the aerials are uniformly distributed along the aerial wire in order to obtain satisfactory emission and uniform distribution of the potential and current along the aerial. The speed of propagation of the field or disturbance along the aerial wire should also be at maximum and as near as possible to the speed of propagation of electromagnetic waves in space.

Waves thus created by such a system would be radiated in space in the two directions which are at right angles to the plane of the aerials. However in order to avoid radiation in one of these two directions a reflector is disposed at a distance equal to or a multiple of of the wave length from the transmitter, which reflector comprises a star of aerials as shown by way of example in Figure 2, at 8, 9', 10', 11', 12, 13, 14' and 15,-

similar to that of the transmitting aerials and each excited in opposite phase to the corresponding transmitting aerial. In this manner all radiation in the undesirable direction is eliminated by means of interference, and emission in the desired direction is reinforced.

The reflector is excited in the same manner as the transmitting system of aerials, the aerials 8, 9', 10, 11, 12, 13, 14 and 15' being also provided with an annular coil 18 through which the electromagnetic .wave travels in the form of a complete wave. The coil of the transmitter and the coil of the reflector are connected together by means of conductor 19 and are designed to have such constants that the electromagnetic wave is transmitted with a proper displacement to produce opposition of phase between the reflector and aerials and the corresponding aerials of the transmitter. In this manner the propagation of electromagnetic waves towards the reflector may be completely neutralized by interference between the waves of the reflector and those of the transmitter. At the same time the propagation in the opposite direction will be increased.

.The number of aerials in the reflector may be greater or less than in the transmitter and in an extreme case may be practically infinite and replaced by a metal plate or other good electrical conductor. Direct excitation of the reflector is also not essential; it may be excited by induction from the transmitter aerials. If a metal plate is employed, it may act as a Hertzian reflector, intercepting at the same time the electromagnetic flux in the desired direction. 1

It is of course commonly known to produce circular polarized waves with wireless transmission by means whose operating characteristics are based on the principle of exciting angularly disposed aerials by two or more circuits in which phase displaced currents through a common genera-tor are produced by using suitably disposed inductances and capacities.

However, the present system of transmission of electromagnetic energy has, among other advantages, over all other heretofore known arrange-- ments of directional wireless transmission, the great advantage that it attains a greater concentration inasmuch as the rotary electromagnetic waves radiated into space tend to retain their direction of propagation apart from any influence of terrestrial electromagnetic fields.

Whirling electromagnetic motion produced laterally of the central axis enlarges the field of electromagnetic wave propagation, the zero field being at a relatively small distance from the said axis. Thus it is impossible outside this restricted field of wave radiation to intercept communications transmitted. The field of electromagnetic wave propagation being thus concentrated, it will be readily understood that the quantity of energy collected at the receiving station will be much greater than in systems hitherto known. The electromagnetic energy received may be utilized as such or converted into mechanical energy.

Variations may be resorted to and parts used without others within thescope of my invention.

Having now fully described my invention, I claim:

1. A directional wireless transmission system adapted for emission of a modulated or an unmodulated rotary electromagnetic field in a highly concentrated beam, comprising a plurality of aerial members interconnected at a common point and projecting therefrom in different directions, a coil coupled with said aerial members and both concentrically disposed with respect to said cornmon point and located within the extremities of said aerial members, and means for causinga progressive wave to flow in said coil, and thereby excite said aerial members.

2. A directional wireless transmission system adapted for emission of a modulated or an unmodulated rotary electromagnetic field in a highly concentrated beam, comprising a plurality of aerials interconnected and radially disposed with respect to a common point and located in a plane substantially perpendicular to the direction of transmission, a substantially annular circuit concentrically disposed with respect to said common point in a plane parallel to said first plane and coupled with said aerials and means for causing a progressive wave to flow in said circular circuit to said aerials.

3. A directional wireless transmission system adapted for emission of a modulated or an unmodulated rotary electromagnetic field in a highly concentrated beam, comprising a plurality of aerials which are connected at, and radially disposed with respect to a common point and located in a plane substantially perpendicular to the direction of transmission, and means for applying a progressive wave to' said aerials for emission therefrom, including a coil of ring formation coupled with said aerials and concentrically disposed about said common point, said aerials being equidistantly spaced so as to form substantially equal angles with each other and also projecting radially beyond said coil.

4. A directional wireless transmission system adapted for emission of a modulated or an'unmodulated rotary electromagnetic field in a highly concentrated beam, comprising a plurality of interconnected radially projecting and equally spaced aerial members, and means for applying a progressive wave to said aerials for emission therefrom, including a coil of ring formation coupled with said aerial members in proximate relation thereto, said aerials projecting radially beyond the outline of said coil.

5. A wireless transmission system according to claim 1 provided with an electromagnetic reflector both similar in construction to the aerial members and the coil coupled therewith and spaced a'distance equal to at least one-fourth of the wave length or a multiple thereof from the aerial members, and which reflector is adapted to produce electromagnetic waves which cancel the electromagnetic waves emitted in a predetermined direction by said transmitting aerial members.

6. A wireless transmission system according to claim 2 provided with an electromagnetic reflector both similar in construction to the aerials andthe annular circuit coupled therewith and spaced a distance equal to at least one-fourth of the wave length or a multiple thereof from the aerials, and which reflector is adapted to produce electromagnetic waves which cancel the electromagnetic waves emitted in a predetermined direction by said transmitting aerials.

'7. A wireless transmission system according to claim 3 provided with an electromagnetic refiector similar in construction to the aerials and the coil coupled therewith and spaced a distance equal to at least one-fourth of the wave length or a multiple thereof from the aerial structure, and which reflector is adapted to produce electromagnetic waves which cancel the electromagnetic waves emitted in a predetermined direction by said transmitting aerial structure.

8. A wireless transmission system according to claim 4 provided with an electromagnetic refiector both similar in construction to the aerial members and the coil capacitatively coupled therewith and spaced a distance equal to at least one-fourth of the wave length or a multiple thereof from the aerial structure, and which reflector is adapted toproduce electromagnetic waves which cancel the electromagnetic waves emitted in a predetermined direction by said SALVATORE SALTO. 

